I read this when I was a kid and it really impressed me: derring-do, occult thrills, a hot dame, and Adolf Hitler. I dipped into it again years later and discovered a fairly pedestrian thriller, but if you're young and looking for seemingly arcane and forbidden reading, this will fill the bill. I read several other Wheatleys and this was, for my teenage (well, pre-teen) money, the best. It spurred a life-long interest in the occult. Though I remain a skeptic, I love reading about the mountebanks and charlatans who populate its byways. "They Used Dark Forces" boasts a nasty magus clearly based on Aleister Crowley, who was a thousand times more interesting than his fictional counterpart here. Still and all, good fun for an undemanding (or naive) reader....